1. Field of the Invention
The present invention relates to the formation, from strip-like stock, of spine strips and to the subsequent registration of the formed strips with cover boards in the course of manufacture of book covers. More particularly, this invention is directed to apparatus which produces, from material being drawn from a supply reel, book cover spine strips of predetermined length and thereafter accurately positions the thus produced spine strips on moving cover boards. Accordingly, the general objects of the general invention are to provide novel and improved apparatus and methods of such character.
2. Description of the Prior Art
In the manufacture of books, covers are formed by applying a spine or center strip to a cover board. The material from which the spine strips are formed is customarily supplied to the book cover production machinery as continuous stock having the appropriate width which is stored on a supply reel. In the prior art book cover production machines, this stock was cut to length by means of apparatus which operated either intermittently or continuously.
In the prior art intermittently operated cutters, the spine strip stock was pulled from the supply reel by means of a transport which included a link-type drive system. The drive system was adjustable so that the spine strip could be cut to the length currently specified. In such pull-off arrangements, tension forces act directly on the supply reel and, during each cutting step, the supply reel is brought to a complete stop. The supply reel will inherently have a significant moment of inertia, and this inertia must be overcome each time the forward feed of the stock is resumed. The tension forces on the supply reel will change as the effective diameter of the reel changes, due to the withdrawal of material therefrom, and the inertia to be overcome for each withdrawal sequence will also change with the change in diameter. The varying tension forces lead to slip and thus to inaccuracies in the cut piece length. Moreover, if the center strip material is narrow and thin, and if this material is furnished on a large diameter supply reel, there is a very significant risk of the strip material breaking as a result of the effort to overcome the moment of inertia.
The spine strip pull-off devices of the type briefly discussed above, which employ link-type drive systems with interposed free wheel mechanisms, are also characterized by a severely limited production rate. Restated, it is difficult to increase the operational speed of these intermittently operated devices because the rate of movement of the strip material is constantly changing.
In the case of proposed devices which advance the spine strip stock material continuously, it has been suggested that the pull-off apparatus include a suction wheel and that the cutting-to-length be accomplished by means of a cross-cutting device consisting of a pair of rotary driven, angled knives. Obviously, for such apparatus to function properly, the rotating cross-cutting knives must be precisely and continuously synchronized with respect to both the advancement speed of the strip material and the currently specified spine strip length. The achievement of such synchronization demands complex and thus expensive apparatus. Furthermore, even if the requisite sychronization could be achieved, there is nevertheless an inherent possibility that length inaccuracy will occur due, by way of example only, to the transporting action of the suction wheel being affected by slip. Additionally, there is a further inherent risk that the moving spine strip material will not be severed precisely at a right-angle to its side edges.
As a further disadvantage of the proposed continuously operating pull-off arrangements for spine strip formation apparatus, the resetting of such devices for different strip lengths entails substantial expense, particularly because such resetting requires skilled and well trained personnel.
Published German Patent Application 36 14 167 discloses apparatus for the manufacture of book covers wherein spine strip stock material is pulled from a supply reel, cut to length by a cross-knife type cutting device, and then supplied to the "cloth cylinder" associated with the book cover machine. In order to achieve the requisite cut length accuracy, in the apparatus of the published application the cutting operation is performed between two transport steps. Thus, a cut length mechanism is provided for driving a system of transport rollers which are installed upstream of the cutting station, the range of constant rotary movement of these transport rollers being adjustable to correspond to the desired cut length. The range of movement is controlled through the use of cams which are installed such that they can be twisted relative to one another.
In the apparatus of German Application 36 14 167, the delivery of the cut-to-length spine strip to the cloth cylinder is accomplished by feeding the strip along a channel under the influence of spaced pairs of rollers which are rotated by a center strip transport mechanism. This center strip transport mechanism is connected to the cut length mechanism through a multiplicity of drive elements. This type of interconnected drive, employing mechanical components to couple two movement sequences, will inherently be deleteriously affected by tolerance errors resulting from inaccuracies in manufacture. At high throughput rates, such errors are particularly detrimental to the cut length accuracy and to the accuracy achieved in the operation in which the spine strip and cover boards are brought together at the cloth cylinder.